1. Field of the Invention
The present invention relates to a method for creating and recording transport time information to be used as time references when transmitting data transport packets recorded in the format of a transport stream in a disk recording medium such as a high-density digital versatile disk (HDVD) to a connected equipment such as a digital television, and a method for transmitting data transport packets on time indicated by the recorded transport time information while reproducing recorded data stream. The present invention also relates to a recording medium embodying information used in these methods.
2. Description of the Related Art
FIG. 1 is a block diagram of a DVD player and a general television which are connected each other. The DVD player 100, which reproduces video and audio data recorded in a disk recording medium such as a DVD-ROM, comprises an optical pickup 12 for detecting signals recorded in a disk 11 such as a DVD-ROM; an analog signal processor 13 for converting the detected high-frequency signals into binary signals; a digital signal processor 14 for processing the binary signals into a program stream (PS) of MPEG standard; a decoder 15 for decoding the data contained in the PS into non-compressed video and audio data and converting them into corresponding analog signals to be applied to the general television 600; a microcomputer 16 controlling operations of the above elements for data reproduction; and a memory 17 for temporally storing data produced while reproduction.
The DVD player 100 configured as FIG. 1 decodes and converts data in the PS reproduced from the disk 11 such as a DVD-ROM into analog video and audio signals, and then applies them to the conventional television 600 for video and audio presentation.
FIG. 2 shows a hierarchical structure of a recorded data stream and time information, especially the presentation timestamp (PTS) and decoding timestamp (DTS), recorded in a read-only disk such as a DVD-ROM.
As shown in FIG. 2, one or more video objects (VOBs) are recorded in a read-only DVD during disk manufacturing. A single VOB is corresponding to a single title or program and is composed of many video object units (VOBUs). A single VOBU is composed of a navigation pack and several data packs. Each data pack consists of a pack header and several program elementary stream packets (PESPs) which contains respective a PES header in which the PTS and DTS information are written.
The audio/video data stream retrieved from the PESPs is decoded on time indicated by the DTS information and then temporarily stored in a memory or a buffer, and outputted to a speaker and a screen of the general television 600 on time indicated by the PTS information.
That is, the point of time when to convert the audio and video data stream reproduced from a read-only DVD is determined based on the DTS and PTS written in the PES header of each PESP, so that the converted analog real audio and video signals can be presented to a viewer through a speaker and a screen of a general television without any discontinuity.
FIG. 3 shows an example of several electric home appliances connected each other through a digital interface such as the IEEE 1394 standard. The electric home appliances connected each other are a digital television (TV) 500; a set top box (STB) 200 for receiving RF broadcast signals, extracting a data stream belonging to a selected program from the broadcast signals, and transmitting the extracted stream to the digital TV 500; and a streamer 300 recording or reproducing a digital data stream to/from a rewritable digital versatile disk (DVD-RAM).
The streamer 300 comprises a stream recording unit 32 for recording transport packets, which constitutes a transport stream (TS) for a digital broadcast program, transmitted from the STB 200 connected through the IEEE 1394 standard in a rewritable DVD 31; a stream reproducing unit 33 for reproducing the TS recorded in the rewritable DVD 31; an interface unit 34 for transmitting the reproduced TS to the STB 200 and receiving a data stream from the STB 200 through the IEEE 1394 standard; a controller 35 for controlling the operations of the above elements; and a memory 35 storing data necessary for the control operation of the controller 35.
The streamer 300 configured as above records a digital data stream of broadcast programs received from the STB 200 in a rewritable DVD in a pre-specified format, or divides a data stream reproduced from the rewritable DVD into transport packets and then transmits them to the STB 200 through the IEEE 1394 standard.
The STB 200 transmits the received transport packets to the digital TV 500, then the digital TV 500 decodes the transport packets to present high-quality video and audio. Such operations make it possible to record digital broadcast programs and reproduce them.
FIG. 4 is a pictorial representation showing a hierarchical structure of a data stream recorded in the rewritable DVD and packet arrival time (PAT) information recorded in each transport packet (TP).
As shown in FIG. 4, one or more stream objects (SOBs) are recorded in a rewritable DVD. A single SOB is composed of many stream object units (SOBUs). Partial stream belonging to a single SOBU is written across several fixed-size sectors. Header information and several TPs are written in each sector.
The streamer 300 adds 4-byte PAT to each TP as shown in FIG. 4 when recording the received data stream. The 4-byte PAT consists of a 9-bit arrival timestamp (ATS) extension marked as ‘ATS_ext’ and a 39-bit arrival timestamp base marked as ‘ATS_base’ according to the MPEG standard. The arrival time extension is a modulo-300 counter that is incremented at a rate of 27 MHz, whereas the arrival time base is incremented at a rate of 90 KHz.
The reason of recording the PAT in each packet as explained above is to transmit recorded packets at same interval which transport packets are received at, and to use the recorded PAT as a position index when searching for the video data, especially the infra-coded picture data recorded in the rewritable DVD. The reason why the position index is necessary is to point the starting point of each infra-coded video frame since the starting point may be located anywhere in a SOBU when the broadcast program is recorded as it is received. The position index is used to jump quickly between infra-coded video frames while a trick play is conducted.
For a recording format for a under-developing read-only HDVD, it may be considered to adopt the TS as the recording-format in consideration that a data stream reproduced from a HDVD-ROM is delivered directly to a digital TV which accepts TS-formatted data.
The HDVD-ROM is not for recording arbitrary broadcast programs but for providing a permanently-recorded program, so that a recorded stream can be divided into many high-density object units (HOBUs) when a HDVD-ROM is manufactured in order that each HOBU may be corresponding to a GOP unit of the MPEG standard.
Each GOP unit always has a infra-coded picture at its leading part, therefore, it is possible to make a trick-play by reproducing infra-coded pictures only by jumping to each HOBU whose position can be known from navigation information read at initial loading of a disk. That is, it is not required to access into transport packet layer, which means that it is not necessary to record PATs like as a REWRITABLE DVD to search for every infra-coded pictures for a trick play.
However, each transport packet should be transmitted at time interval specified when a program is recorded into a read-only disk to be presented without discontinuity or delay, therefore, time reference information to use as point of time when to transmit each packet is still required for a read-only disk.
However, if such time reference information is written in every transport packet for a HDVD-ROM, the space for program data may be remarkably decreased.
Accordingly, a method for recording time information to use as a packet sending time reference without decreasing program recording area should be developed urgently.